OPS-6704-mongodb-template-workaround (#32)

Workaround for a problem with the ionoscloud_mongo_template DataSource.

modules/ionos-mongodb-cluster/README.md

@@ -5,6 +5,7 @@
 | Name | Version |
 |------|---------|
 | <a name="provider_ionoscloud"></a> [ionoscloud](#provider\_ionoscloud) | 6.4.18 |
+| <a name="provider_null"></a> [null](#provider\_null) | n/a |
 ## Modules
 
 | Name | Source | Version |
@@ -52,4 +53,5 @@
 | [ionoscloud_mongo_cluster.mongo_cluster](https://registry.terraform.io/providers/ionos-cloud/ionoscloud/6.4.18/docs/resources/mongo_cluster) | resource |
 | [ionoscloud_mongo_user.initial_mongo_user](https://registry.terraform.io/providers/ionos-cloud/ionoscloud/6.4.18/docs/resources/mongo_user) | resource |
 | [ionoscloud_mongo_template.mongo_template](https://registry.terraform.io/providers/ionos-cloud/ionoscloud/6.4.18/docs/data-sources/mongo_template) | data source |
+| [null_data_source.template_workaround](https://registry.terraform.io/providers/hashicorp/null/latest/docs/data-sources/data_source) | data source |
 <!-- END_TF_DOCS -->

modules/ionos-mongodb-cluster/data.tf

@@ -1,4 +1,15 @@
 data "ionoscloud_mongo_template" "mongo_template" {
   count = var.resource_template == null ? 0 : 1
   name = var.resource_template
+}
+
+# Workaround
+# There's probably a bug in the IONOS Provider: The DataSource ionoscloud_mongo_template doesn't define id
+# as computed, leading to an inconsistent final plan (id is null instead of unknown in the initial plan)
+# This null_data_source is in between and the output is unknown in the initial plan, solving the problem.
+data "null_data_source" "template_workaround" {
+  inputs = {
+    mongo_template_id = var.resource_template == null ? null : data.ionoscloud_mongo_template.mongo_template[0].id
+  }
+  depends_on = [ data.ionoscloud_mongo_template.mongo_template ]
 }

modules/ionos-mongodb-cluster/main.tf

@@ -16,7 +16,7 @@ resource ionoscloud_mongo_cluster "mongo_cluster" {
     cidr_list     = local.cidrs
   }
 
-  template_id = var.resource_template == null ? null : data.ionoscloud_mongo_template.mongo_template[0].id
+  template_id = data.null_data_source.template_workaround.outputs["mongo_template_id"]
   edition     = var.resource_template == null ? "enterprise" : null
 
   maintenance_window {